1. Field of the Invention
This invention relates to more particularly a hydraulic type pump and to a tubular diaphragm pump of unique features to lift liquids, such as hydrocarbons, from subsurface reservoirs communicating with the earth's surface by way of cased boreholes.
2. Description of the Prior Art
Very few of the wells completed flow free of their own accord. Approximately 90% require some means of artificial lifting system to bring the wanted liquids such as hydrocarbons to the surface. The method and equipment chosen depend upon the depth of the well, the nature of the sand, and of course the cost involved. Lifting methods and apparatus fall into one of two general categories: surface and subsurface.
The rod pump system is in wide use. The "horse head" bobbing up and down is a familiar sight in oil fields around the world, and this method and apparatus of bringing oil to the surface accounts for some 80% of artificial lifting done. The heart of this type of system is the sucker rod which acts much like a flexible spring and operates under great stress. The sucker rods can be easily damaged by improper handling, and any bends, nicks, or dents can lead to metal fatique and early failure. The failure of the sucker rod requires that the rods be pulled from the well tubing at significant labor cost.
Another method of bringing liquids to the surface is by means of an electrically powered submersible pump. A centrifugal pump, together with its driving motor, is lowered down the well bore to the bottom of the well. Power is transmitted through an electrical cable from a surface control box. The pressure created by rotation of the pump's impellers then force the fluid to the surface. Because of the large power demands, problems have arisen from the failure of insulated power cable. Today, the use of the submersible pump is limited because of the expense of the system.
Subsurface hydraulic pumping has also been employed. Such a system and technique uses the oil in the field to force additional oil to the surface. A pump is located at the bottom of the well and driven by a hydraulic motor. On the surface, a standard engine-driven pump draws clean crude oil from the top of a settling tank and forces it down through tubing to the hydraulic motor. The oil, under pressure, drives the motor which in turn drives the pump. The driving oil is exhaused from the motor into the well where it mixes with the oil to be pumped and the pressure from the pump lifts both to the surface through a second string of tubing.
Tubular diaphragm pumps have been proposed in the past for a variety of uses. Typical of such apparatus is the equipment described in U.S. Pat. No. 3,951,572 utilized for the purpose of pumping cement slurry and comprised of two pumps connected in parallel. Obviously, the apparatus described in the foregoing patent is unsuitable for moving liquids from a subsurface reservoir which communicates to the earth's surface by way of a cased borehole.
There has been a need for a less labor intensive and less expensive system for lifting oil from subsurface reservoirs. Such need is satisfied by the present invention.